Thin-film transistor, display unit, and electronic apparatus

ABSTRACT

A thin-film transistor includes: a gate electrode; a gate insulating film disposed on the gate electrode; an oxide semiconductor layer disposed on the gate insulating film and having a channel region located to face the gate electrode; a channel protective layer disposed on the gate insulating film and the oxide semiconductor layer; and source and drain electrodes each connected to the oxide semiconductor layer through a connection hole formed in the channel protective layer, in which the oxide semiconductor layer has, in a part of the channel region, a narrow region with a narrower width than a width of the connection hole.

BACKGROUND

The present disclosure relates to a thin-film transistor using an oxidesemiconductor, a display unit including the thin-film transistor, and anelectronic apparatus including the display unit.

It is known that oxides of zinc, indium, gallium, tin, and mixturesthereof (hereinafter referred to as “oxide semiconductors”) exhibitfavorable semiconductor properties, and in recent years, applications ofthe oxide semiconductors to thin-film transistors (hereinafter referredto as “TFTs”) as drive devices of active matrix display units have beenactively studied. For example, a mixed oxide of zinc, indium, andgallium (hereinafter referred to as “IGZO”) exhibits electron mobility10 or more times as high as that of amorphous silicon used as asemiconductor in related art; therefore, applications of IGZO tolarge-screen high-definition high-frame-rate liquid crystal displayunits and organic EL display units are strongly desired.

For the formation of a bottom-gate TFT, it is proposed to form a channelprotective layer on an entire surface of an oxide semiconductor layerand to connect source and drain electrodes to the oxide semiconductorlayer through connection holes (contact holes) formed in the channelprotective layer (for example, refer to Japanese Unexamined PatentApplication Publication No. 2010-135462). By doing so, the TFT is formedwith use of fewer masks while protecting the oxide semiconductor layerby the channel protective film during a process of forming the TFT.

SUMMARY

However, in the method described in Japanese Unexamined PatentApplication Publication No. 2010-135462, a channel width (W) isdetermined by a width of the connection hole formed in the channelprotective layer; therefore, the channel width may vary due tovariations in etching of the channel protective layer, and there isstill room for improvement.

It is desirable to provide a thin-film transistor capable of suppressingvariations in channel width, a display unit including the thin-filmtransistor, and an electronic apparatus.

According to an embodiment of the disclosure, there is provided athin-film transistor including: a gate electrode; a gate insulating filmdisposed on the gate electrode; an oxide semiconductor layer disposed onthe gate insulating film and having a channel region located to face thegate electrode; a channel protective layer disposed on the gateinsulating film and the oxide semiconductor layer; and source and drainelectrodes each connected to the oxide semiconductor layer through aconnection hole formed in the channel protective layer, in which theoxide semiconductor layer has, in a part of the channel region, a narrowregion with a narrower width than a width of the connection hole.

Here, “width” means a dimension in a channel width direction. Thechannel width direction is a direction orthogonal to a channel length (adistance between source and drain electrodes) direction.

In the thin-film transistor according to the embodiment of thedisclosure, since the narrow region with a narrower width than the widthof the connection hole is disposed in a part of the channel region ofthe oxide semiconductor layer, a channel width (W) is determined by thewidth of the narrow region. Therefore, even if the width of theconnection hole is varied due to variations in etching of the channelprotective layer, variations in the channel width are suppressed.

According to an embodiment of the disclosure, there is provided adisplay unit including a display device and a thin-film transistordriving the display device, the thin-film transistor including: a gateelectrode; a gate insulating film disposed on the gate electrode; anoxide semiconductor layer disposed on the gate insulating film andhaving a channel region located to face the gate electrode; a channelprotective layer disposed on the gate insulating film and the oxidesemiconductor layer; and source and drain electrodes each connected tothe oxide semiconductor layer through a connection hole formed in thechannel protective layer, in which the oxide semiconductor layer has, ina part of the channel region, a narrow region with a narrower width thana width of the connection hole.

In the display unit according to the embodiment of the disclosure, thedisplay device is driven by the thin-film transistor according to theabove-described embodiment of the disclosure in which variations in thechannel width are suppressed. Therefore, variations in transistorcharacteristics caused by variations in the channel width are reduced tosuppress a decline in display quality such as luminance unevenness.

According to an embodiment of the disclosure, there is provided anelectronic apparatus with a display unit including a display device anda thin-film transistor driving the display device, the thin-filmtransistor including: a gate electrode; a gate insulating film disposedon the gate electrode; an oxide semiconductor layer disposed on the gateinsulating film and having a channel region located to face the gateelectrode; a channel protective layer disposed on the gate insulatingfilm and the oxide semiconductor layer; and source and drain electrodeseach connected to the oxide semiconductor layer through a connectionhole formed in the channel protective layer, in which the oxidesemiconductor layer has, in a part of the channel region, a narrowregion with a narrower width than a width of the connection hole.

In the electronic apparatus according to the embodiment of thedisclosure, a display operation is performed by the display unitaccording to the above-described embodiment of the disclosure.

In the thin-film transistor according to the embodiment of thedisclosure, since the narrow region with a narrower width than the widthof the connection hole is disposed in a part of the channel region ofthe oxide semiconductor layer, variations in the channel width caused byvariations in etching of the channel protective layer is suppressible.Therefore, when the display unit or the electronic apparatus isconfigured with use of the thin-film transistor, high-quality display isachievable by the thin-film transistor with reduced variations incharacteristics caused by variations in the channel width.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the technology, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a diagram illustrating a configuration of a display unitaccording to a first embodiment of the disclosure.

FIG. 2 is an equivalent circuit diagram illustrating an example of apixel drive circuit illustrated in FIG. 1.

FIG. 3 is a sectional view illustrating a configuration of a TFTillustrated in FIG. 2.

FIG. 4 is a plan view illustrating a configuration of the TFTillustrated in FIG. 3.

FIG. 5 is a plan view selectively illustrating an oxide semiconductorlayer and a connection hole illustrated in FIG. 4.

FIG. 6 is a sectional view illustrating a configuration of a displayregion illustrated in FIG. 1.

FIGS. 7A and 7B are sectional views illustrating a method ofmanufacturing the display unit illustrated in FIG. 1 in order.

FIGS. 8A and 8B are diagrams illustrating manufacturing processesfollowing FIGS. 7A and 7B.

FIG. 9 is a diagram illustrating a manufacturing process following FIGS.8A and 8B.

FIGS. 10A to 10C are plan views for describing a disadvantage of athin-film transistor in related art.

FIG. 11 is a plan view illustrating a configuration of a thin-filmtransistor according to Modification 1.

FIG. 12 is a plan view illustrating a configuration of a thin-filmtransistor according to Modification 2.

FIG. 13 is a plan view illustrating a configuration of a thin-filmtransistor according to Modification 3.

FIG. 14 is a plan view illustrating a configuration of a thin-filmtransistor according to Modification 4.

FIG. 15 is a diagram illustrating a configuration of a display unitaccording to a second embodiment of the disclosure.

FIG. 16 is a diagram illustrating an equivalent circuit of a pixelillustrated in FIG. 15.

FIG. 17 is a sectional view illustrating a configuration of a displayregion illustrated in FIG. 15.

FIG. 18 is a sectional view illustrating a configuration of a displayunit according to a third embodiment of the disclosure.

FIG. 19 is a plan view illustrating a configuration of a drive substrateillustrated in FIG. 18.

FIG. 20 is a sectional view illustrating a configuration of a displayregion illustrated in FIG. 19.

FIGS. 21A and 21B are sectional views illustrating a method ofmanufacturing the display unit illustrated in FIG. 18 in sequence.

FIG. 22 is a plan view illustrating a schematic configuration of amodule including any one of the display units according to theabove-described embodiments.

FIGS. 23A and 23B are perspective views illustrating an appearance ofApplication Example 1 of any one of the display units according to theabove-described embodiments.

FIG. 24 is a perspective view illustrating an appearance of ApplicationExample 2.

FIG. 25 is a perspective view illustrating an appearance of ApplicationExample 3.

FIGS. 26A and 26B are perspective views illustrating an appearance ofApplication Example 4 from a front side and a back side, respectively.

FIG. 27 is a perspective view illustrating an appearance of ApplicationExample 5.

FIG. 28 is a perspective view illustrating an appearance of ApplicationExample 6.

FIGS. 29A to 29G illustrate Application Example 7, where FIGS. 29A and29B are a front view and a side view in a state in which ApplicationExample 7 is opened, respectively, and FIGS. 29C, 29D, 29E, 29F, and 29Gare a front view, a left side view, a right side view, a top view, and abottom view in a state in which Application Example 7 is closed,respectively.

DETAILED DESCRIPTION

Preferred embodiments of the disclosure will be described in detailbelow referring to the accompanying drawings. It is to be noted thatdescription will be given in the following order.

1. First Embodiment (Organic EL display unit; an example in which anarrow region is disposed in a part of a channel region, and corners ofan oxide semiconductor layer protrude from source and drain electrodes)

2. Modification 1 (An example in which two sides facing each other in achannel width direction of the oxide semiconductor layer protrude fromthe source and drain electrodes)

3. Modification 2 (An example in which one of two sides facing eachother in the channel width direction of the oxide semiconductor layerprotrudes from the source and drain electrodes)

3. Modification 3 (An example in which the oxide semiconductor layer isexposed from an channel protective layer and the source and drainelectrodes in a part of a connection hole)

4. Modification 4 (An example adopting a combination of Modifications 1and 3)

5. Second Embodiment (Liquid crystal display unit)

6. Third Embodiment (Electronic paper display unit)

7. Application Examples (Module, electronic apparatuses)

First Embodiment

FIG. 1 illustrates a configuration of a display unit according to afirst embodiment of the disclosure. The display unit is used as anultra-thin organic light-emitting color display unit or the like, andhas, on a TFT substrate 1 which will be described later, a displayregion 110 in which pixels PXLC configured of a plurality of organiclight-emitting devices 10R, 10G, and 10B which will be described lateras display devices are arranged in a matrix. A horizontal selector(HSEL) 121 as a signal section, and a write scanner (WSCN) 131 and apower supply scanner (DSCN) 132 as scanner sections are disposed aroundthe display region 110.

In the display region 110, signal lines DTL101 to DTL10 n are arrangedin a column direction, and scanning lines WSL101 to WSL10 m and powersupply lines DSL101 to DSL10 m are arranged in a row direction. A pixelcircuit 140 including the pixel PXLC (any one of the organiclight-emitting devices 10R, 10G and 10B (sub-pixels)) is disposed at anintersection of each signal line DTL and each scanning line WSL. Thesignal lines DTL are connected to the horizontal selector 121, and imagesignals are supplied from the horizontal selector 121 to the signallines DTL. The scanning lines WSL are connected to the write scanner131. The power supply lines DSL are connected to the power supplyscanner 132.

FIG. 2 illustrates an example of the pixel circuit 140. The pixelcircuit 140 is an active drive circuit including a sampling transistor3A and a driving transistor 3B, a retention capacitor 3C, and alight-emitting device 3D configured of the pixel PXLC. A gate of thesampling transistor 3A is connected to a corresponding scanning lineWSL101, and one of a source and a drain of the sampling transistor 3A isconnected to a corresponding signal line DTL101, and the other of themis connected to a gate g of the driving transistor 3B. A drain d of thedriving transistor 3B is connected to a corresponding power supply lineDSL101, and a source s of the driving transistor 3B is connected to ananode of the light-emitting device 3D. A cathode of the light-emittingdevice 3D is connected to ground wiring 3H. It is to be noted that theground wiring 3H is installed as common wiring for all of the pixelsPXLC. The retention capacitor 3C is connected between the source s andthe gate g of the driving transistor 3B.

The sampling transistor 3A is brought into conduction based on a controlsignal supplied from the scanning line WSL101 to sample a signalpotential of an image signal supplied from the signal line DTL and thento retain the signal potential in the retention capacitor 3C. Thedriving transistor 3B receives a current from the power supply lineDSL101 which is maintained at a power supply potential to supply a drivecurrent to the light-emitting device 3D based on the signal potentialretained in the retention capacitor 3C. The light-emitting device 3Demits light with luminance according to the signal potential of theimage signal by the drive current supplied from the driving transistor3B.

FIG. 3 illustrates a sectional configuration of the TFT 20 configuringthe sampling transistor 3A illustrated in FIG. 2. Moreover, FIG. 3 alsoillustrates the retention capacitor 3C illustrated in FIG. 2. It is tobe noted that the driving transistor 3B illustrated in FIG. 2 has aconfiguration similar to the TFT 20 illustrated in FIG. 3.

The TFT 20 is, for example, an oxide semiconductor transistor includinga gate electrode 21, a gate insulating film 22, an oxide semiconductorlayer 23, a channel protective layer 24, a source electrode 25S, and adrain electrode 25D in this order on a substrate 10. Here, an “oxidesemiconductor” is an oxide of any one of zinc, indium, gallium, and tinor an oxide of a mixture thereof, and it is known that the oxidesemiconductor exhibits favorable semiconductor characteristics.

The gate electrode 21 controls electron density in the oxidesemiconductor layer 23 by a gate voltage applied to the TFT 20, and hasa thickness of, for example, about 200 nm or less, and is made of, forexample, molybdenum (Mo).

The gate insulating film 22 is configured of, for example, a siliconoxide film with a thickness of about 300 nm or less. Moreover, the gateinsulating film 22 may be configured of a laminate film including asilicon oxide film and a silicon nitride film.

The oxide semiconductor layer 23 has a thickness of, for example, about40 nm, and is made of, for example, indium gallium zinc oxide (IGZO(In—Ga—Zn-Oxide)). As the material of the oxide semiconductor layer 23,in addition to IGZO, indium tin zinc oxide (ITZO) as an amorphous oxidesemiconductor may be used. As a crystalline oxide semiconductor, zincoxide (ZnO), indium zinc oxide (IZO (registered trademark), indiumgallium oxide, (IGO), ITO, indium oxide (InO), or the like may be used.

It is to be noted that, if necessary, a protective film (not illustratedin FIG. 3, refer to FIG. 7B) may be disposed on the oxide semiconductorlayer 23. The protective film is configured of, for example, a siliconoxide film with a thickness of about 50 nm.

The channel protective layer 24 is a stopper layer protecting a channelregion in a process of etching the source electrode 25S and the drainelectrode 25D. The channel protective layer 24 is configured of, forexample, a silicon oxide film with a thickness of about 200 nm.

The source electrode 25S and the drain electrode 25D each are connectedto the oxide semiconductor layer 23 through a connection hole 24A formedin the channel protective layer 24. The source electrode 25S and thedrain electrode 25D each are configured of any one of metals such asmolybdenum, aluminum, and titanium, or a multilayer film of the metals.Preferably, an example of specific configurations of the sourceelectrode 25S and the drain electrode 25D is a laminate film including amolybdenum layer 25A with a thickness of about 50 nm, an aluminum layer25B with a thickness of about 200 nm to 1 μm both inclusive, and atitanium layer 25C with a thickness of about 50 nm in this order ofcloseness to the oxide semiconductor layer 23. It is to be noted thatthe source electrode 25S and the drain electrode 25D each may beconfigured of a laminate film including a molybdenum layer, an aluminumlayer, and a molybdenum layer, or a laminate film including a titaniumlayer, an aluminum layer, and a titanium layer, depending on the use andapplication of the TFT 20.

It is to be noted that an entire surface of the TFT 20 may be coveredwith a passivation film (not illustrated), if necessary. The passivationfilm is made of a material similar to that of the gate insulating film22 or the channel protective layer 24.

The retention capacitor 3C includes, for example, a lower electrode 31located at the same level as the gate electrode 21, an insulating film32 located at the same level as the gate insulating film 22, and anupper electrode 33 extending from the drain electrode 25D. It is to benoted that the oxide semiconductor layer 23 is also included in theretention capacitor 3C to reduce a difference in level between theretention capacitor 3C and the TFT 20.

FIG. 4 illustrates a planar configuration of the TFT 20 illustrated inFIG. 3 viewed from the source electrode 25S and the drain electrode 25D.In FIG. 4, a region where the oxide semiconductor layer 23 is disposedis shaded, and a region where the channel protective layer 24 isdisposed is marked with diagonally right-down lines. FIG. 5 selectivelyillustrates the oxide semiconductor layer 23 and the connection hole 24Aillustrated in FIG. 4.

The oxide semiconductor layer 23 has a channel region 23A located toface the gate electrode 21. A narrow region 23B is disposed in a part(for example, a central part in a channel length direction) of thechannel region 23A. A width W23 of the narrow region 23B is narrowerthan a width W24 of the connection hole 24A. Therefore, in the TFT 20,variations in a channel width W are suppressed.

In other words, when the narrow region 23B is provided, the channelwidth W of the TFT 20 is determined by the width W23 of the narrowregion 23B. Therefore, the channel width W is dimensionally stabilizedirrespective of variations in the width W24 of the connection hole 24Ain a manufacturing process. It is to be noted that a distance betweentwo connection holes 24A is equal to a channel length L of the TFT 20.

The width W23 of the narrow region 23B is preferably determined to benarrower than the width W24 of the connection hole 24A, even if thewidth W24 of the connection hole 24A is minimized in consideration ofvariations in the width W24 of the connection hole 24A in themanufacturing process.

Moreover, the oxide semiconductor layer 23 has wide regions 23C inregions other than the narrow region 23B (regions on both sides of thenarrow region 23B). The wide regions 23C are source and drain regions,that is, regions to which the source electrode 25S or the drainelectrode 25D is connected through the connection hole 24A.

The wide regions 23C preferably have protruding portions 23D whichprotrude from the source electrode 25S and the drain electrode 25D andare located at four corners which surround the narrow region 23B. Theprotruding portions 23D serve as oxygen inlets in a recovery annealing(oxygen supply) process which will be described later on the oxidesemiconductor layer 23, allowing transistor characteristics to beefficiently recovered for a short time.

FIG. 6 illustrates a sectional configuration of the display region 110.In the display region 110, the organic light-emitting devices 10Remitting red light, the organic light-emitting devices 10G emittinggreen light, and the organic light-emitting devices 10B emitting bluelight are formed in order in a matrix as a whole. It is to be noted thatthe organic light-emitting devices 10R, 10G, and 10B each have arectangular planar shape, and one pixel is configured of a combinationof adjacent organic light-emitting devices 10R, 10G, and 10B.

The organic light-emitting devices 10R, 10G, and 10B each have aconfiguration in which an anode 52, an inter-electrode insulating film53, an organic layer 54 including a light-emitting layer which will bedescribed later, and a cathode 55 are laminated in this order on the TFTsubstrate 1 with a planarization insulating film 51 in between.

Such organic light-emitting devices 10R, 10G, and 10B are covered with aprotective film 56 such as a silicon nitride film or a silicon oxidefilm, if necessary, and a sealing substrate 71 made of glass or the likeis bonded to an entire surface of the protective film 56 with anadhesive layer 60 made of a thermosetting resin or an ultravioletcurable resin in between to seal the organic light-emitting devices 10R,10G, and 10B. A color filter 72 and a light-shielding film 73 as a blackmatrix may be disposed on the sealing substrate 71, if necessary.

The planarization insulating film 51 planarizes a surface of the TFTsubstrate 1 where the pixel circuits 140 each of which includes thesampling transistor 3A and the driving transistor 3B each configured ofthe above-described TFT 20 are formed. The planarization insulating film51 is preferably made of a material with high pattern accuracy, since aminute connection hole 51A is formed in the planarization insulatingfilm 51. Examples of the material of the planarization insulating film51 include organic materials such as polyimide and inorganic materialssuch as silicon oxide (SiO₂). The driving transistor 3B illustrated inFIG. 2 is electrically connected to the anode 52 through the connectionhole 51A formed in the planarization insulating film 51.

The anode 52 is formed corresponding to each of the organiclight-emitting devices 10R, 10G, and 10B. Moreover, the anode 52 has afunction as a reflective electrode reflecting light emitted from thelight-emitting layer, and preferably has as high reflectivity aspossible to enhance light emission efficiency. The anode 52 has athickness of, for example, about 100 nm to 1000 nm both inclusive, andis made of a simple substance or an alloy of a metal element such assilver (Ag), aluminum (Al), chromium (Cr), titanium (Ti), iron (Fe),cobalt (Co), nickel (Ni), molybdenum (Mo), copper (Cu), tantalum (Ta),tungsten (W), platinum (Pt), or gold (Au).

The inter-electrode insulating film 53 secures insulation between theanode 52 and the cathode 55, and allows a light emission region to beaccurately formed in a desired shape. The inter-electrode insulatingfilm 53 is made of, for example, an organic material such as polyimideor an inorganic insulating material such as silicon oxide (SiO₂). Theinter-electrode insulating film 53 has an opening corresponding to alight emission region of the anode 52. It is to be noted that theorganic layer 54 and the cathode 55 may be continuously disposed notonly on the light emission region but also on the inter-electrodeinsulating film 53; however, light is emitted only from the opening ofthe inter-electrode insulating film 53.

The organic layer 54 has a configuration in which, for example, a holeinjection layer, a hole transport layer, the light-emitting layer, andan electron transport layer (all not illustrated) are laminated in thisorder of closeness to the anode 52; however, these layers other than thelight-emitting layer may be included, if necessary. Moreover, theorganic layer 54 may have a configuration different for each of colorsemitted from the organic light-emitting devices 10R, 10G, and 10B. Thehole injection layer enhances hole injection efficiency and is a bufferlayer for preventing leakage. The hole transport layer enhances holetransport efficiency to the light-emitting layer. The light-emittinglayer emits light by the recombination of electrons and holes inresponse to the application of an electric field. The electron transportlayer enhances electron transport efficiency to the light-emittinglayer. It is to be noted that the material of the organic layer 54 maybe a typical low-molecular or polymer organic material, and is notspecifically limited.

The cathode 55 has, for example, a thickness of about 5 nm to 50 nm bothinclusive, and is made of a simple substance or an alloy of a metalelement such as aluminum (Al), magnesium (Mg), calcium (Ca), or sodium(Na). In particular, an alloy of magnesium and silver (an MgAg alloy) oran alloy of aluminum (Al) and lithium (Li) (an AlLi alloy) ispreferable. Moreover, the cathode 55 may be made of ITO or IZO (indiumzinc oxide (registered trademark)).

The display unit may be manufactured by the following process, forexample.

Forming TFT Substrate 1

FIGS. 7A and 7B to FIG. 9 illustrate a method of manufacturing the TFT20 in sequence. It is to be noted that FIGS. 7A and 7B to FIG. 9illustrate processes of manufacturing the TFT 20 on the left andprocesses of manufacturing a portion where wiring lines intersect withor overlap each other (for example, a portion where the scanning lineWSL and the signal line DTL intersect with or overlap each other) on theright.

First, the TFT 20 including the oxide semiconductor layer 23 is formedon the substrate 10 to form the TFT substrate 1. More specifically, amolybdenum film with a thickness of about 200 nm or less is formed onthe substrate 10 made of glass by, for example, a sputtering method.Next, photolithography and etching are subjected to the molybdenum film.Thus, as illustrated in FIG. 7A on the left, the gate electrode 21 isformed in a region where the TFT 20 is to be formed. Moreover, asillustrated FIG. 7A on the right, wiring lines located at the same levelas the electrode 21 (for example, the scanning lines WSL) are formed inthe portion where the wiring lines intersect with or overlap each other.

Next, referring again to FIG. 7A, the gate insulating film 22 configuredof a silicon oxide film with a thickness of about 300 nm or less isformed on an entire surface of the substrate 10 by, for example, a CVD(Chemical Vapor Deposition) method.

After that, an IGZO film (not illustrated) with a thickness of about 40nm and a silicon oxide film (not illustrated) with a thickness of about50 nm are formed on the gate insulating film 22, and the IGZO film andthe silicon oxide film are formed into predetermined shapes by, forexample, photolithography and etching. Thus, as illustrated in FIG. 7Bon the left, the oxide semiconductor layer 23 and the protective film 26are formed in the region where the TFT 20 is to be formed. At this time,the narrow region 23B is formed in a part of the channel region 23A ofthe oxide semiconductor layer 23. On the other hand, as illustrated inFIG. 7B on the right, in the portion where the wiring lines intersectwith or overlap on each other, the oxide semiconductor layer 23 and theprotective film 26 are removed.

It is to be noted that the oxide semiconductor layer 23 may be formedthrough directly performing photolithography and etching on the IGZOfilm without using the protective film 26.

After the oxide semiconductor layer 23 is formed, as illustrated in FIG.8A, a silicon oxide film 24B is formed on the gate insulating film 22,the oxide semiconductor layer 23, and the protective film 26 by, forexample, a CVD method.

Next, the silicon oxide film 24B and the protective film 26 are formedinto predetermined shapes by, for example, photolithography and etching.Thus, as illustrated in FIG. 8B, the channel protective layer 24 havingthe connection holes 24A is formed.

After that, a molybdenum layer 25A with a thickness of about 50 nm, analuminum layer 25B with a thickness of about 500 nm, and a titaniumlayer 25C with a thickness of about 50 nm are formed by, for example, asputtering method, and then are formed into predetermined shapes byphotolithography and etching. Thus, as illustrated in FIG. 9 on theleft, the source electrode 25S and the drain electrode 25D are formed inthe region where the TFT 20 is to be formed. The source electrode 25Sand the drain electrode 25D are connected to the oxide semiconductorlayer 23 through the connection holes 24A. Thus, the TFT 20 illustratedin FIG. 3 is formed. On the other hand, as illustrated in FIG. 9 on theright, wiring lines (for example, the signal lines DTL) located at thesame level as the source electrode 25S and the drain electrode 25D areformed in the portion where the wiring lines intersect with or overlapeach other.

As illustrated in FIGS. 4 and 5, since the narrow region 23B is disposedin a part of the channel region 23A of the oxide semiconductor layer 23,the channel width W of the TFT 20 is determined by the width W23 of thenarrow region 23B. Therefore, even if the width W24 of the connectionhole 24A varies due to variations in etching of the channel protectivelayer 24, variations in the channel width W of the TFT 20 aresuppressed.

On the other hand, in related art, as illustrated in FIG. 10A, a channelwidth W of a TFT 120 is determined by a width of a connection hole 124Aformed in a channel protective layer (not illustrated). Therefore, asillustrated in FIG. 10B, when the etching amount of the connection hole124A is increased, the channel width W of the TFT 120 is increased. Onthe other hand, as illustrated in FIG. 10C, when the etching amount ofthe connection hole 124A is reduced, the channel width W of the TFT 120is reduced. In other words, the channel width W of the TFT 120 variesdue to variations in etching of the channel protective layer (notillustrated). It is to be noted that, components in FIGS. 10A to 10Ccorresponding to components of the TFT 20 illustrated in FIG. 4 aregiven the same numerals incremented by 100. Moreover, in FIGS. 10A to10C, the region where the channel protective layer is disposed is notshaded (refer to FIG. 4).

After the source electrode 25S and the drain electrode 25D illustratedin FIG. 9 are formed, the recovery annealing (oxygen supply) process onthe oxide semiconductor layer 23 is performed. Thus, a defect developedin the oxide semiconductor layer 23 during the manufacturing process isrecovered. Here, the protruding portions 23D protruding from the sourceelectrode 25S and the drain electrode 25D are disposed at four corners,which surround the narrow region 23B, of the wide regions 23C.Therefore, the protruding portions 23D serve as oxygen inlets, allowingtransistor characteristics to be efficiently recovered for a short time.

Thus, the TFT substrate 1 including the TFTs 20 illustrated in FIG. 3 isformed.

Forming Organic Light-Emitting Devices 10R, 10G, and 10B

Next, the display region 110 configured of the organic light-emittingdevices 10R, 10G, and 10B is formed above the TFTs 20. In other words,first, an entire surface of the TFT substrate 1 is coated with aphotosensitive resin, and the photosensitive resin is subjected toexposure and development to form the planarization insulating film 51and the connection holes 51A, and then the planarization insulating film51 is baked. Next, the anodes 52 made of the above-described materialare formed by, for example, DC sputtering, and are selectively etchedwith use of, for example, lithography to be patterned into apredetermined shape. Next, the inter-electrode insulating film 53 madeof the above-described material with the above-described thickness isformed by, for example, a CVD method, and openings are formed in theinter-electrode insulating film 53 with use of, for example,lithography. After that, the organic layer 54 and the cathode 55 made ofthe above-described materials are formed in order by, for example, anevaporation method to form the organic light-emitting devices 10R, 10G,and 10B. Next, the organic light-emitting devices 10R, 10G, and 10B arecovered with the protective film 56 made of the above-describedmaterial.

After that, the adhesive layer 60 is formed on the protective film 56.Then, the sealing substrate 71 on which the color filter 72 and thelight-shielding film 73 are disposed and which is made of theabove-described material is prepared to be bonded to the TFT substrate 1with the adhesive layer 60 in between. Thus, the display unitillustrated in FIG. 6 is completed.

In the display unit, the sampling transistor 3A is brought intoconduction based on the control signal supplied from the scanning lineWSL to sample a signal potential of an image signal supplied from thesignalling DTL and then to retain the signal potential in the retentioncapacitor 3C. A current is supplied to the driving transistor 3B fromthe power supply line DSL which is maintained at a power supplypotential, and a drive current is supplied to the light-emitting device3D (the organic light-emitting device 10R, 10G, or 10B) based on thesignal potential retained in the retention capacitor 3C. Thelight-emitting device 3D (the organic light-emitting device 10R, 10G, or10B) emits light with luminance according to the signal potential of theimage signal by the drive current supplied from the driving transistor3B. The light passes through the cathode 55, the color filter 72, andthe sealing substrate 71 to be extracted.

Since the narrow region 23B with a narrower width than that of theconnection hole 24A is disposed in a part of the channel region 23A ofthe oxide semiconductor layer 23, the channel width W of the TFT 20 isdetermined by the width W23 of the narrow region 23B, and variations inthe channel width W are suppressed. Therefore, variations in transistorcharacteristics caused by variations in the channel width W are reducedto suppress a decline in display quality such as luminance unevenness.

Thus, in the embodiment, the narrow region 23B with a narrower widththan that of the connection hole 24A is disposed in a part of thechannel region 23A; therefore, the influence of variations in the widthW24 of the connection hole 24A caused by variations in etching of thechannel protective layer 24 is eliminated, and the channel width W isdimensionally stabilized accordingly. Therefore, variations intransistor characteristics due to variations in the channel width W arereduced to enhance display quality.

Moreover, the protruding portions 23D protruding from the sourceelectrode 25S and the drain electrode 25D are disposed at four corners,which surround the narrow region 23B, of the wide regions 23C as regionsother than the narrow region 23B; therefore, in the recovery annealing(oxygen supply) process on the oxide semiconductor layer 23, oxygen issupplied from the protruding portions 23D to recover the transistorcharacteristics for a short time.

Modification 1

It is to be noted that, in the above-described embodiment, the casewhere the protruding portions 23D are disposed at four corners, whichsurround the narrow region 23B, of the wide regions 23C is described;however, the protruding portion 23D may be disposed at one or morecorners or one or more sides of each of the wide regions 23C, and thearrangement of the protruding portions 23D is not specifically limited.

For example, as illustrated in FIG. 11, the protruding portions 23D maybe disposed on both sides, which face each other in the channel widthdirection, of each of the wide regions 23C. In this modification, theprotruding portions 23D are disposed on four sides of the wide regions23C; therefore, in the recovery annealing (oxygen supply) process on theoxide semiconductor layer 23, oxygen supply efficiency is enhanced, andtransistor characteristics are recovered for a shorter time. It is to benoted that, in FIG. 11 and following drawings, a region where thechannel protective layer 24 is disposed is not shaded (refer to FIG. 4).

Modification 2

Moreover, for example, as illustrated in FIG. 12, the protruding portion23D may be disposed on one (for example, a bottom side) of sides, whichface each other in the channel width direction, of each of the wideregions 23C. In this modification, the protruding portions 23D aredisposed on two sides of the wide regions 23C; therefore, as inModification 1, in the recovery annealing (oxygen supply) process on theoxide semiconductor layer 23, oxygen supply efficiency is enhanced, andtransistor characteristics are recovered for a shorter time.

It is to be noted that, although not illustrated, the protrudingportions 23D may be disposed on a top side of the sides, which face eachother in the channel width direction, of each of the wide regions 23C.

Modification 3

Further, for example, in the above-described embodiment, the case wherethe source electrode 25S and the drain electrode 25D fill in the entireconnection holes 24A is described; however, as illustrated in FIG. 13,an edge of the source electrode 25S and an edge of the drain electrode25D may be disposed in the connection holes 24A. In this case, the oxidesemiconductor layer 23 has exposed portions 23E exposed from the channelprotective layer 24, the source electrode 25S, and the drain electrode25D in parts of the connection holes 24A. Like the protruding portions23D, the exposed portions 23E may serve as oxygen inlets in the recoveryannealing (oxygen supply) process on the oxide semiconductor layer 23.Therefore, transistor characteristics are efficiently recovered for ashort time.

It is to be noted that, in this modification, the oxide semiconductorlayer 23 is preferably made of a crystalline oxide semiconductor such aszinc oxide (ZnO), indium zinc oxide (IZO (registered trademark)), indiumgallium oxide (IGO), ITO, or indium oxide (InO), because etchingselectivity with respect to the source electrode 25S and the drainelectrode 25D is able to be increased.

Modification 4

In addition, for example, as illustrated in FIG. 14, a combination ofModification 1 and Modification 3 may be used. In other words, the oxidesemiconductor layer 23 may have the protruding portions 23D and theexposed portions 23E. It is to be noted that, although not illustrated,a combination of Modification 2 and Modification 3 may be used.

Second Embodiment

FIG. 15 illustrates an entire configuration of a display unit accordingto a second embodiment of the disclosure. The display unit is used as aliquid crystal television or the like, and has, on the above-describedTFT substrate 1, the display region 110 in which pixels PXLC configuredof a plurality of liquid crystal display devices 10L which will bedescribed later as display devices are arranged in a matrix. A datadriver 121A as a signal section, and a gate driver 131A as a scannersection are disposed around the display region 110. An illuminationsection 150 as a backlight unit is disposed on a backside of the displayregion 110.

FIG. 16 illustrates an equivalent circuit of the pixel PXLC. The pixelPXLC includes the TFT 20 described in the first embodiment, the liquidcrystal display device 10L, and a capacitor Cst.

The TFT 20 has a function as a switching device supplying an imagesignal to the pixel PXLC, and has a configuration similar to the TFT 20in the first embodiment. A gate of the TFT 20 is connected to a gate busline GL extending in a horizontal direction. A source bus line SLextending in a vertical direction is disposed orthogonal to the gate busline GL. A source of the TFT 20 is connected to the source bus line SL,and a drain of the TFT 20 is connected to one end of the liquid crystaldisplay device 10L and one end of the capacitor Cst.

The liquid crystal display device 10L has a function as a display deviceperforming an operation for display based on a signal voltage suppliedthrough the TFT 20. The other end of the liquid crystal display device10L is grounded.

The capacitor Cst generates a potential difference between both endsthereof, and more specifically, the capacitor Cst includes a dielectricaccumulating a charge. The other end of the capacitor Cst is connectedto a capacitor bus line CL extending parallel to the gate bus line GL,that is, in the horizontal direction.

FIG. 17 illustrates a sectional configuration of the display region 110.As in the first embodiment, the TFT substrate 1 includes the TFTs 20including the oxide semiconductor layer 23 (refer to FIG. 3) on thesubstrate 10. Each of the liquid crystal display devices 10L includes apixel electrode 82A made of, for example, ITO on a planarizationinsulating film 81. Moreover, a color filter 84 configured of redfilters 84R, green filters 84G, and blue filters 84B, a light-shieldingfilm 85, and a common electrode 82B made of, for example, ITO aredisposed on a counter substrate 83. A liquid crystal layer 82C isdisposed between the pixel electrodes 82A and the common electrode 82B.It is to be noted that the capacitor Cst is not illustrated in FIG. 17.

The planarization insulating film 81 has a configuration similar to theplanarization insulating film 51 in the first embodiment. The TFT 20 isconnected to the pixel electrode 82A through a connection hole 81Aformed in the planarization insulating film 81.

The display unit may be manufactured by the following process, forexample.

Forming TFT Substrate 1

First, in a manner similar to the first embodiment, the TFTs 20including the oxide semiconductor layer 23 are formed on the substrate10 to form the TFT substrate 1.

Forming Liquid Crystal Display Device 10L

Next, the display region 110 configured of the liquid crystal displaydevices 10L is formed above the TFTs 20. In other words, first, anentire surface of the TFT substrate 1 is coated with a photosensitiveresin, and the photosensitive resin is subjected to exposure anddevelopment to form the planarization insulating film 81 and theconnection holes 81A, and then the planarization insulating film 81 isbaked. Next, the pixel electrodes 82A made of the above-describedmaterial are formed by, for example, DC sputtering, and are selectivelyetched with use of, for example, lithography to be patterned into apredetermined shape.

Moreover, the color filter 84, the light-shielding film 85, and thecommon electrode 82B made of the above-described material are formed onthe counter substrate 83, and the TFT substrate 1 and the countersubstrate 83 are bonded together with a sealing frame (not illustrated)in between. After that, a liquid crystal is injected from an opening(not illustrated) of the sealing frame to form the liquid crystal layer82C between the pixel electrodes 82A and the common electrode 82B, andthe opening is sealed. Thus, the display unit illustrated in FIG. 17 iscompleted.

In the display unit, light from the illumination section 150 isuniformly diffused by an optical sheet (not illustrated) to enter eachof the liquid crystal display devices 10L. The incident light passesthrough the liquid crystal layer 82C while being modulated in each pixelbased on an image voltage applied between each of the pixel electrodes82A and the common electrode 82B. The light having passed through theliquid crystal layer 82C passes through the color filter 84 to exit fromthe counter substrate 83 as color display light.

Functions and effects in this embodiment are similar to those in thefirst embodiment.

Third Embodiment

FIG. 18 illustrates a sectional configuration of a display unitaccording to a third embodiment of the disclosure. The display unit isan electrophoretic display unit (a so-called electronic paper displayunit) displaying an image (for example, textual information) with use ofan electrophoresis phenomenon, and includes a display layer 91, acounter substrate 92, a transparent adhesive layer 93, and a protectivefilm 94 in this order on the TFT substrate 1. It is to be noted thatFIG. 18 schematically illustrates a shape of the display unit, anddimensions and shapes in FIG. 18 are different from actual dimensionsand shapes.

As illustrated in FIG. 19, in the TFT substrate 1, an adhesive region110A is disposed around the display region 110 located at a center ofthe TFT substrate 1 to completely surround the display region 110. Thedisplay layer 91 is disposed on the display region 110, and an edge ofthe protective film 94 is adhered to the adhesive region 110A by anadhesive layer 94A.

The TFT substrate 1 includes a barrier layer 90B and a TFT (Thin-FilmTransistor) circuit 90C laminated in this order on a base 90A. The base90A is made of, for example, an inorganic material such as glass,quartz, silicon, or gallium arsenide, a metal material such as stainlesssteel, or a plastic material such as polyimide, polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polymethylmethacrylate (PMMA), polycarbonate (PC), polyether sulfone (PES),polyethyletherketone (PEEK), aromatic polyester (liquid crystalpolymer). The base 90A may be a base with stiffness such as a wafer, ora base with flexibility such as thin-layer glass, a film, or metal foil.When the base 90A has flexibility, a flexible display unit isachievable. The base 90A has, for example, a thickness (a thickness in alaminate direction, hereinafter simply referred to as “thickness”) ofabout 10 μm to 100 μm both inclusive.

The barrier layer 90B is an AlO_(x)N_(1-x) film, where X is 0.01 to 0.2,or a silicon nitride (Si₃N₄) film formed by, for example, a CVD method,and suppresses degradation in the TFT circuit 90C and the display layer91 caused by moisture or an organic gas. The barrier layer 90B is formedby a CVD method in many cases, and compared to the case where thebarrier layer 90B is formed by an evaporation method, the barrier layer90B formed by CVD is dense and has lower moisture permeability.

The TFT circuit 90C has a switching function for selecting a pixel. TheTFT circuit 90C is configured of the TFTs 20 described referring to FIG.3 in the first embodiment.

FIG. 20 illustrates a sectional configuration of the display region 110illustrated in FIG. 19. The display layer 91 includes an electrophoreticdisplay body 91C between pixel electrodes 91A and a common electrode91B. Each of the pixel electrodes 91A is connected to the TFT circuit90C through a connection hole 95A of a planarization insulating film 95.The display layer 91 has, for example, a thickness in the laminatedirection of about 40 μm to 165 μm both inclusive. Each of the pixelelectrodes 91A is disposed for each pixel, and is made of, for example,a simple substance or an alloy of a metal element such as chromium (Cr),gold (Au), platinum (Pt), nickel (Ni), copper (Cu), tungsten (W),aluminum (Al), or silver (Ag). The common electrode 91B is disposed onone entire surface of the counter substrate 92, and is made of, forexample, a translucent conductive material (a transparent electrodematerial) such as indium oxide-tin oxide (ITO), antimony oxide-tin oxide(ATO), fluorine-doped tin oxide (FTO), or aluminum-doped zinc oxide(AZO).

The counter substrate 92 is disposed on the display region 110 in amanner similar to the display layer 91, and has, for example, athickness of about 125 μm. In this embodiment, an image is displayed onthe counter substrate 92; therefore, a light-transmissive material isused for the counter substrate 92, and except for this, a materialsimilar to that of the base 90A may be used for the counter substrate92.

The protective film 94 seals the display layer 91. The protective film94 has, in addition to a moisture-proof function, an optical functionsuch as an antireflection function or an anti-glare function, and aprotection function against external force, and has, for example, athickness of about several hundreds of μm.

The protective film 94 is fixed to the counter substrate 92 by thetransparent adhesive layer 93. The transparent adhesive layer 93 is madeof an OCA (Optical Clear Adhesive) or the like with a thickness of about25 μm. When the base 90A is configured of a flexible substrate, thetransparent adhesive layer 93 is preferably also flexible.

A gap 95 is disposed between the display region 110 and the adhesiveregion 110A which are sealed by the protective film 94 (between sidesurfaces of the display layer 91 and the counter substrate 92, and theprotective film 94), and the side surfaces of the display layer 91 andthe counter substrate 92 are surrounded by the gap 95.

The display unit may be manufactured by the following process, forexample.

Forming TFT Substrate 1

FIGS. 21A and 21B illustrates a method of manufacturing the display unitin sequence. First, as illustrated in FIG. 21A, the barrier layer 90Bmade of silicon nitride is formed on the base 90A by, for example, a CVDmethod. Next, referring again to FIG. 21A, the TFT circuit 90Cconfigured of the TFTs 20 including the oxide semiconductor layer 23 isformed on the barrier layer 90B to form the TFT substrate 1. The TFTs 20may be formed in a similar manner to the first embodiment.

Forming Electrophoretic Display Layer 91

After the TFT substrate 1 is formed, a metal film made of, for example,chromium, gold, platinum, nickel, copper, tungsten, aluminum, or silveris formed on an entire surface of the TFT substrate 1, and the metalfilm is patterned to form the pixel electrodes 91A.

Next, as illustrated in FIG. 21B, the display body 91C is formed on thecounter substrate 92 including the common electrode 91B by, for example,coating, and then the counter substrate 92 is bonded to the TFTsubstrate 1. Thus, the display layer 91 and the counter substrate 92 areformed on the TFT substrate 1. The common electrode 91B is formedthrough forming a film made of, for example, ITO on one entire surfaceof the counter substrate 92.

After the counter substrate 92 is bonded, the protective film 94 isfixed on the counter substrate 92 by the transparent adhesive layer 93.At this time, the protective film 94 having all sides larger than allsides of the display region 110 and an area larger than that of thedisplay region 110 is used. Thus, a portion protruding outside thedisplay region 110 is formed in the protective film 94. Next, theportion protruding from the display region 110 of the protective film 94is bended toward the TFT substrate 1 to be fixed to the adhesive region110A of the TFT substrate 1 by the adhesive layer 94 to cover sidesurfaces of the display layer 91. Thus, the display unit illustrated inFIGS. 18 to 20 is completed.

In the display unit, display is performed by the electrophoretic displaybody 91C based on an image voltage applied between the pixel electrodes91A and the common electrode 91B in the display layer 91.

Functions and effects in this embodiment are similar to those in thefirst embodiment.

Application Examples

Next, referring to FIGS. 22 to 29, application examples of the displayunits according to the above-described embodiments will be describedbelow. The display units according to the above-described embodimentsare applicable to electronic apparatuses, in any fields, such astelevisions, digital cameras, notebook personal computers, portableterminal units such as cellular phones and smartphones, and videocameras. In other words, the display units are applicable to electronicapparatuses, in any fields, displaying an image signal supplied fromoutside or an image signal produced inside as an image or a picture.

Module

Any one of the display units according to the above-describedembodiments is incorporated into various electronic apparatuses such asApplication Examples 1 to 7 which will be described later, for example,as a module as illustrated in FIG. 22. In the module, for example, aregion 160 exposed from the sealing substrate 71 and the adhesive layer60 in the first embodiment or from the counter substrate 83 in thesecond embodiment is provided on a side of the substrate 10, and anexternal connection terminal (not illustrated) is formed in the exposedregion 160 through extending the wiring of the horizontal selector 121,the write scanner 131, and the power supply scanner 132 in the firstembodiment or through extending the data driver 121A and the gate driver131A in the second embodiment. A flexible printed circuit (FPC) 161 forsignal input and output may be connected to the external connectionterminal.

Application Example 1

FIGS. 23A and 23B illustrate an appearance of an electronic book towhich any one of the display units according to the above-describedembodiments is applied. The electronic book includes a display section210 and a non-display section 220, and the display section is configuredof any one of the display units according to the above-describedembodiments.

Application Example 2

FIG. 24 illustrates an appearance of a smartphone to which any one ofthe display units according to the above-described embodiments isapplied. The smartphone includes, for example, a display section 230 anda non-display section 240, and the display section 230 is configured ofany one of the display units according to the above-describedembodiments.

Application Example 3

FIG. 25 illustrates an appearance of a television to which any one ofthe display units according to the above-described embodiments isapplied. The television includes, for example, an image display screensection 300 including a front panel 310 and a filter glass 320, and theimage display screen section 300 is configured of any one of the displayunits according to the above-described embodiments.

Application Example 4

FIGS. 26A and 26B illustrate an appearance of a digital camera to whichany one of the display units according to the above-describedembodiments is applied. The digital camera includes, for example, alight-emitting section 410 for a flash, a display section 420, a menuswitch 430, and a shutter button 440, and the display section 420 isconfigured of any one of the display units according to theabove-described embodiments.

Application Example 5

FIG. 27 illustrates an appearance of a notebook personal computer towhich any one of the display units according to the above-describedembodiments is applied. The notebook personal computer includes, forexample, a main body 510, a keyboard 520 for operation of inputtingcharacters and the like, and a display section 530 for displaying animage, and the display section 530 is configured of any one of thedisplay units according to the above-described embodiments.

Application Example 6

FIG. 28 illustrates an appearance of a video camera to which any one ofthe display units according to the above-described embodiments isapplied. The video camera includes, for example, a main body 610, a lens620 provided on a front surface of the main body 610 and for shooting animage of an object, a shooting start/stop switch 630, and a displaysection 640, and the display section 640 is configured of any one of thedisplay units according to the above-described embodiments.

Application Example 7

FIGS. 29A to 29G illustrate an appearance of a cellular phone to whichany one of the display units according to the above-describedembodiments is applied. The cellular phone has a configuration in which,for example, a top-side enclosure 710 and a bottom-side enclosure 720are connected together through a connection section (hinge section) 730,and the cellular phone includes a display 740, a sub-display 750, apicture light 760, and a camera 770. The display 740 or the sub-display750 is configured of any one of the display units according to theabove-described embodiments.

Although the present disclosure is described referring to theembodiments, the disclosure is not limited thereto, and may be variouslymodified. For example, in the above-described embodiments, the materialand thickness of each layer, the method and conditions of forming eachlayer are not limited to those described in the above-describedembodiments, and each layer may be made of any other material with anyother thickness by any other method under any other conditions.

Moreover, in the above-described embodiments, specific configurations ofthe organic light-emitting devices 10R, 10B, and 10G are described;however, it is not necessary for the organic light-emitting devices 10R,10B, and 10G to include all of the layers described in the embodiments,and the organic light-emitting devices 10R, 10B, and 10G may furtherinclude any other layer.

Further, the present disclosure is applicable to not only a display unitincluding the organic light-emitting devices but also a display unitincluding any other display devices such as liquid crystal displaydevices, inorganic electroluminescence devices, or electrodeposition orelectrochromic display devices.

In addition, for example, specific configurations of the display unitsare described in the above-described embodiments; however, it is notnecessary for the display units to include all of the componentsdescribed in the embodiments, and the display units may further includeany other component.

It is to be noted that the technology is allowed to have the followingconfigurations.

(1) A thin-film transistor including:

a gate electrode;

a gate insulating film disposed on the gate electrode;

an oxide semiconductor layer disposed on the gate insulating film andhaving a channel region located to face the gate electrode;

a channel protective layer disposed on the gate insulating film and theoxide semiconductor layer; and

source and drain electrodes each connected to the oxide semiconductorlayer through a connection hole formed in the channel protective layer,

in which the oxide semiconductor layer has, in a part of the channelregion, a narrow region with a narrower width than a width of theconnection hole.

(2) The thin-film transistor according to (1), in which the oxidesemiconductor layer has a protruding portion protruding from the sourceand drain electrodes at one or more corners or one or more sides of awide region which is a region other than the narrow region.

(3) The thin-film transistor according to (2), in which the protrudingportion is disposed on each of four corners, which surround the narrowregion, of the wide region.

(4) The thin-film transistor according to (2), in which the protrudingportion is disposed on one or both of sides, which face each other in achannel width direction, of the wide region.

(5) The thin-film transistor according to any one of (1) to (4), inwhich the oxide semiconductor layer has, in a part of the connectionhole, an exposed portion exposed from the channel protective layer andthe source and drain electrodes.

(6) A display unit including a display device and a thin-film transistordriving the display device, the thin-film transistor including:

a gate electrode;

a gate insulating film disposed on the gate electrode;

an oxide semiconductor layer disposed on the gate insulating film andhaving a channel region located to face the gate electrode;

a channel protective layer disposed on the gate insulating film and theoxide semiconductor layer; and

source and drain electrodes each connected to the oxide semiconductorlayer through a connection hole formed in the channel protective layer,

in which the oxide semiconductor layer has, in a part of the channelregion, a narrow region with a narrower width than a width of theconnection hole.

(7) An electronic apparatus with a display unit including a displaydevice and a thin-film transistor driving the display device, thethin-film transistor including:

a gate electrode;

a gate insulating film disposed on the gate electrode;

an oxide semiconductor layer disposed on the gate insulating film andhaving a channel region located to face the gate electrode;

a channel protective layer disposed on the gate insulating film and theoxide semiconductor layer; and

source and drain electrodes each connected to the oxide semiconductorlayer through a connection hole formed in the channel protective layer,

in which the oxide semiconductor layer has, in a part of the channelregion, a narrow region with a narrower width than a width of theconnection hole.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application No. 2012-021502 filed in theJapan Patent Office on Feb. 3, 2012, the entire content of which ishereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A thin-film transistor comprising: a gateelectrode; a gate insulating film disposed on the gate electrode; anoxide semiconductor layer disposed on the gate insulating film andhaving a channel region located to face the gate electrode; a channelprotective layer disposed on the gate insulating film and the oxidesemiconductor layer; and source and drain electrodes each connected tothe oxide semiconductor layer through a connection hole formed in thechannel protective layer, wherein the oxide semiconductor layer has, ina part of the channel region, a narrow region with a narrower width thana width of the connection hole.
 2. The thin-film transistor according toclaim 1, wherein the oxide semiconductor layer has a protruding portionprotruding from the source and drain electrodes at one or more cornersor one or more sides of a wide region which is a region other than thenarrow region.
 3. The thin-film transistor according to claim 2, whereinthe protruding portion is disposed on each of four corners, whichsurround the narrow region, of the wide region.
 4. The thin-filmtransistor according to claim 2, wherein the protruding portion isdisposed on one or both of sides, which face each other in a channelwidth direction, of the wide region.
 5. The thin-film transistoraccording to claim 1, wherein the oxide semiconductor layer has, in apart of the connection hole, an exposed portion exposed from the channelprotective layer and the source and drain electrodes.
 6. A display unitincluding a display device and a thin-film transistor driving thedisplay device, the thin-film transistor comprising: a gate electrode; agate insulating film disposed on the gate electrode; an oxidesemiconductor layer disposed on the gate insulating film and having achannel region located to face the gate electrode; a channel protectivelayer disposed on the gate insulating film and the oxide semiconductorlayer; and source and drain electrodes each connected to the oxidesemiconductor layer through a connection hole formed in the channelprotective layer, wherein the oxide semiconductor layer has, in a partof the channel region, a narrow region with a narrower width than awidth of the connection hole.
 7. An electronic apparatus with a displayunit including a display device and a thin-film transistor driving thedisplay device, the thin-film transistor comprising: a gate electrode; agate insulating film disposed on the gate electrode; an oxidesemiconductor layer disposed on the gate insulating film and having achannel region located to face the gate electrode; a channel protectivelayer disposed on the gate insulating film and the oxide semiconductorlayer; and source and drain electrodes each connected to the oxidesemiconductor layer through a connection hole formed in the channelprotective layer, wherein the oxide semiconductor layer has, in a partof the channel region, a narrow region with a narrower width than awidth of the connection hole.